TW201623637A - Hearth roll and continuous annealing facility - Google Patents

Abstract

Provided is a hearth roll that supports and conveys a steel sheet in a continuous annealing furnace, wherein: the entirety of a shaft part and a roll main body is constituted by a ceramic material, more specifically, the shaft part and a roll main body are constituted by ceramic layers that are formed of different types of ceramic material and that have a concentric circular shape with the center thereof being the roll rotation axis; and the hearth roll not only excels in pickup resistance but has a long roll life and over a long period of time doesn't require maintenance. Also provided is a continuous annealing facility that uses the hearth roll in at least one of a heating zone, a soaking zone, and a cooling zone.

Description

Hearth roll and continuous annealing equipment

The present invention relates to a hearth roll in which a continuous heat treatment is applied while conveying a steel sheet in a continuous annealing furnace, and a continuous annealing apparatus using the hearth roll.

In the continuous annealing apparatus, after the steel sheet in the coiled state is returned to the plate shape on the entry side, the steel sheet is guided to a furnace which is kept at a high temperature, and is supported by a roller or the like while being conveyed, and a continuous heat treatment is applied. It is cooled and taken out of the furnace, and then taken up again as a coil, thereby applying a continuous heat treatment to the steel sheet; in recent years, an annealing apparatus such as a cold-rolled steel sheet, a stainless steel sheet, or an electromagnetic steel sheet has been widely used.

A hearth roll that is placed in a furnace of the continuous annealing facility and that is carried while supporting a steel sheet is conventionally manufactured using heat-resistant steel or a heat-resistant alloy. However, since the hearth roll is used in an oxidizing or reducing environment for a long period of time in a furnace maintained at a high temperature of 700 to 1300 ° C, deformation (bending) or pick-up of the roll is liable to occur. Problems. Here, the term "adhesive" (also referred to as "build-up") refers to iron, iron oxide, manganese oxide, etc. on the surface of the steel sheet, and accumulated in the hearth. If the adhesion occurs, the steel plate supported and transported by the hearth roller will cause defects, which will seriously damage the quality of the product.

Therefore, as a technique for solving the above problems, a method has been developed in which a ceramic is sprayed on a surface of a metal roll base material, or a ceramic sleeve or a carbon sleeve is attached to a metal roll. For example, Patent Document 1 discloses a hearth roll for a heat treatment furnace which is attached to a surface portion of a base made of heat-resistant cast steel and has a spray coating made of zirconium oxide and is resistant to chipping. And the high-temperature peeling resistance and the high-temperature abrasion resistance are excellent; the zirconium oxide contains zirconium oxide ZrSi ₂ as a whole 10 to 70 vol%, and the remaining part contains MgO, CaO, and 5 to 20% by weight. One or more of Y ₂ O ₃ . Further, Patent Document 2 discloses a hearth roll which is attached to a metal roll shaft and is provided with a ceramic sleeve, and in order to suppress cracking which is likely to occur when the sleeve is fixed, the sleeve is two. At least one of the ends is pressed by the pressing member that is seated by the roller shaft in the axial direction, and is disposed in a coiled state between the inner surface and the outer surface of both end portions of the sleeve. There are metal sheets. Further, Patent Document 3 discloses a hearth roll for a heat treatment furnace which is attached to a metal core body and is fitted with a carbon sleeve having adhesive resistance.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Laid-Open Patent Publication No. 06-065708

[Patent Document 2] Japanese Patent Laid-Open No. 01-176021

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2005-281791

However, in the case of the roll of a metal roll base material disclosed in Patent Document 1, a ceramic roll is excellent in adhesion resistance. However, depending on the furnace temperature or environment of the annealing furnace, peeling is likely to occur, so that it is suitable. The scope is limited. In addition, the ceramic spray coating is easily worn by friction with the steel sheet, and the replacement cycle of the rolls is only a few years, which causes maintenance problems. Further, the roll having the ceramic sleeve attached to the metal roll shaft disclosed in Patent Document 2 is excellent in adhesion resistance. However, since it is necessary to externally attach the sleeve to the metal roller shaft, it is necessary to replace the roller in a short period of six months or so, when the fixing portion is broken or a roller which is caused by a difference in thermal expansion between the metal and the ceramic is bent. Repair the fixed part. Further, a hearth roll equipped with a carbon sleeve other than Patent Document 3 also has the same problem.

As described above, the conventional hearth rolls have problems in terms of durability, and it is necessary to frequently replace or repair the rolls, which is a considerable burden on equipment maintenance.

The present invention has been made in view of the above problems in the prior art, and an object thereof is to provide a hearth roll which is excellent in not only excellent in adhesion resistance, long in roll life, long-term maintenance, and use of the above-described hearth roll Continuous annealing equipment.

The inventors of the present invention have focused on constituting a furnace in order to solve the aforementioned problems. The material of the bed roller is repeatedly studied. As a result, it has been found that the present invention can be obtained by forming the hearth roll as a whole from one or more types of ceramics, thereby obtaining a hearth roll which is resistant to adhesion and which is not required to be maintained for a long period of time.

That is, the present invention is a hearth roll which is a hearth roll for supporting and transporting a steel sheet in a continuous annealing furnace, characterized in that the shaft portion of the hearth of the hearth and the body of the roll are made of ceramic.

The hearth roll of the present invention is composed of different types of ceramics and is formed of a concentric circular ceramic layer centered on the rotating shaft of the roll.

Further, in the hearth roll of the present invention, the shaft portion and the roller body are made of different types of ceramics.

Further, in the hearth roll of the present invention, the roller body is composed of different types of ceramic layers.

Further, in the hearth roll of the present invention, the ceramic has a high-temperature strength of 200 MPa or more and a thermal shock resistance of 350 ° C or more.

Further, in the above-described hearth roll of the present invention, the coefficient of thermal expansion in the temperature range of use of the inner layer ceramic of the outer layer ceramic is in the range of 0.5 to 1.5.

Further, in the hearth roll of the present invention, the ceramic is any one of tantalum nitride, tantalum carbide, aluminum oxide, and zirconium oxide.

Further, the present invention is a continuous annealing apparatus characterized in that the hearth roll according to any one of the preceding claims is used for one or more of a heating belt, a soaking belt, and a cooling belt.

In addition, the foregoing continuous annealing apparatus of the present invention is The hearth roll is used in the heating zone, the soaking zone, and the cooling zone in the furnace at a temperature of 700 to 1300 °C.

According to the present invention, since the entire portion of the hearth roll and the roll body of the continuous annealing apparatus is composed of one or more kinds of ceramics, in addition to suppressing adhesion and greatly improving the surface quality of the steel sheet of the product, Since the deformation of the hearth roll can be greatly reduced, it is possible to replace the hearth roll for more than 10 years, which not only enables maintenance-free, but also contributes greatly to the improvement of productivity.

1‧‧‧ steel plate

2‧‧‧heating belt

3‧‧‧All tropical

4‧‧‧Cooling belt

5‧‧‧ hearth roll

5a‧‧‧Axis

5b‧‧‧roll body

Fig. 1 is a view showing an example of a structure of a hearth roll of the present invention.

Fig. 2 is a view for explaining an outline of a continuous annealing apparatus to which a hearth roll of the present invention can be applied.

Fig. 1 is a view schematically showing a state in which a horizontal (horizontal type) continuous annealing apparatus which applies a continuous heat treatment while heating a steel sheet while being conveyed in a horizontal direction is opened by the inlet side. The steel sheet 1 recovered from the coil by the pay-off reel (PR) is subjected to heat treatment for heating, soaking, and cooling while continuously passing through the heating belt 2, the heat-receiving belt 3, and the cooling belt 4. Tension reel by the exit side (tension reel, TR) is again taken as a coil. Further, although not shown in Fig. 1, between the unwinding reel and the heating belt 2, a fusion splicer which is used for continuously plate leaping, and a rolling oil from the steel sheet are generally disposed. The cleaning device or the looper device is removed, and a circulation device or a temper rolling device is generally disposed between the cooling belt 4 and the tension reel.

The heating belt 2 or the soaking zone 3 is a heat treatment for applying a desired material to a steel sheet as a material to be treated, and generally the furnace temperature is heated to a temperature of 700 ° C or more and 1300 ° C or less. Further, the heating of the heating belt 2 is usually performed by a direct fire heating method in which a direct flame is sprayed on a steel sheet or an inter-connected heating method using a radiant tube; and the heating of the tropics 3 is mostly performed by using a radiant tube or an electric heater. The heating method is connected.

The hearth roll 5 that supports and transports the steel sheet in the furnace of the heating belt 2, the heat tropic zone 3, and the cooling zone 4 is generally a shaft portion 5a that becomes a rotation center of the roller as shown in Fig. 2, and A roller body 5b formed around the shaft portion and having a peripheral surface that is in contact with the steel sheet; conventionally used as a measure for resisting adhesion, it is mainly used around a shaft portion made of heat-resistant steel, and is made of ceramic or carbon. The hearth roll of the sleeve. However, the above-described hearth roll system is excellent in adhesion resistance, but the roll life is short due to roll deformation or wear, and it is necessary to frequently perform maintenance such as replacement or repair of the roll.

Therefore, in the present invention, the entire hearth roll including the shaft portion and the roller body is composed only of ceramics, thereby solving the above problems.

Here, examples of the ceramic which can be used in the hearth roll of the present invention include cerium nitride Si ₃ N ₄ , lanthanum carbide SiC, alumina Al ₂ O ₃ , zirconia ZrO ₂ , and the like. Any one of them can be applied. Further, the hearth roll is basically a hollow roll, but may be a solid roll.

Among the above ceramics, it is preferred to use a high-temperature strength of 200 MPa or more and a thermal shock resistance of 350 ° C or more.

If the high-temperature strength is less than 200 MPa, the stress may be destroyed when the stress is concentrated on the part of the roller. Further, if the thermal shock resistance is less than 350 ° C, the temperature at which the furnace is opened due to maintenance may be limited. Stop time growth. The high-temperature strength is 300 MPa or more, and the thermal shock resistance is preferably 700 ° C or more.

Here, the term "high-temperature strength" means a bending strength at a temperature of 1300 ° C measured by a method specified in JIS R1604.

In addition, the thermal shock resistance refers to a temperature difference which is measured by the method specified in JIS R1648 and does not cause cracking during rapid cooling.

Incidentally, as a reference, the representative values of the high-temperature strength and the thermal shock resistance of the ceramics are shown in Table 1 together with the thermal expansion coefficient described later. However, as a preferred roll material, from the viewpoint of thermal shock resistance It is preferred to use tantalum nitride Si ₃ N ₄ or tantalum carbide SiC.

Further, the hearth roll of the present invention may be constituted by using only one of the above-described ceramics or only one type of ceramic in which the ceramic is mixed, but may be formed using two or more kinds of ceramics having different characteristics. However, in the case of being composed of two or more kinds of ceramics, a multilayer structure in which a plurality of ceramic layers having a concentric shape around the roll axis is formed is preferable.

An example of the multilayer structure as described above may be, for example, a shaft portion that serves as a rotating shaft of the roller, and a roller body that is a peripheral portion (a portion in contact with the steel sheet) of the shaft portion, and the ceramic type is different. Alternatively, the roller body may be a multilayer structure formed by a plurality of different ceramic layers.

However, in the case of the multilayer structure as described above, it is preferred that the ratio of the coefficient of thermal expansion of the inner layer ceramic to the outer layer ceramic is from 0.5 to 1.5. If the ratio of the coefficient of thermal expansion of the outer layer to the inner layer is larger than the above range, stress is generated due to a difference in thermal expansion, which causes cracking (destruction). On the other hand, if it is intended to be smaller than the above range, it is understood from the values of the thermal expansion coefficients described in Table 1 that the difference in thermal expansion coefficient between the types of ceramics is large, which may not be achieved. A better ratio of thermal expansion coefficients is in the range of 0.9 to 1.1. Further, the coefficient of thermal expansion is measured by a method specified in JIS R1618, and an example of measurement of one of linear expansion coefficients between 40 and 400 ° C is a rough value.

Here, in the case where the hearth roll has a multilayer structure of three or more layers, it is preferable to satisfy the above relationship among all the layers, for example, in the case of a three-layer structure in which the outer layer, the middle layer, and the inner layer are formed, not only the outer layer and the middle layer. In the middle and inner layers It is also preferable to satisfy the aforementioned relationship.

Moreover, as a method of manufacturing the hearth roll formed by the multilayer structure, a shrink fit method, a mechanical pin fixing method, or the like may be used, and any method may be used.

The hearth roll of the present invention which satisfies the above conditions can be suitably used as a hearth roll of a continuous annealing furnace. In particular, the hearth roll of the present invention is excellent not only in adhesion resistance, high-temperature strength, and impact resistance, but also excellent in abrasion resistance due to friction with a steel sheet, so that it is suitably used in a furnace at a temperature of 700 to 1300. Heating zone, uniformity, and cooling zone in the °C section. If the temperature in the furnace is less than 700 ° C, adhesion will not occur, and thermal shock resistance and high temperature strength are not necessary, so the conventional hearth roll can be fully coped. On the other hand, when it exceeds 1300 ° C, the strength of the steel sheet is lowered due to the approach to the melting point, and it is difficult to pass through. Further, the effect of the hearth roll of the present invention is most effective in the case where the temperature in the furnace is 1000 ° C or higher.

Here, in the continuous annealing apparatus, although the steel sheet is supported by the hearth of the hearth, the horizontal furnace (horizontal furnace) is conveyed in a horizontal direction and applied in one direction, and the steel sheet is passed through the hearth roll in the furnace. The hearth furnace to which the heat treatment is applied while reversing the conveyance direction several times can be applied to any of the hearth rolls of the present invention. However, in the case of a hearth roll used in a vertical furnace, it is necessary to avoid bending strain on the steel sheet when the conveyance direction is reversed, so that the roll diameter (diameter) is generally as large as several hundred mm. The manufacture of a hearth roll of such a large diameter only with ceramics causes an increase in the cost of the roll. Therefore, the hearth roll of the present invention, although for use 300mm The following horizontal continuous annealing equipment for small-diameter hearth rolls is preferably used, but if it is possible to make a large diameter due to technological advancement, it can also be suitably used for vertical continuous annealing equipment.

[Examples]

The horizontal continuous annealing equipment for the cold-rolled steel sheet formed by the equipment shown in Fig. 1 is provided with a hearth roll in a heating belt and a temperature range of 800 ° C or higher in a soaking furnace, and is continuously used for one year. The change of the eccentricity of the roller and the friction of the outer peripheral surface of the roller are measured; the hearth roller, the shaft portion and the roller body are formed only by tantalum nitride Si ₃ N ₄ , and the shaft diameter is 40 mm. The outer diameter of the sleeve is 150mm The length of the roller body is 2600 mm. Further, the continuous annealing apparatus has a maximum temperature of 1150 ° C in the heating zone and the soaking zone during operation.

Here, the amount of the eccentricity of the roller refers to the amount of change in the position of the outer peripheral surface when the roller is rotated, and the maximum value when the entire length of the roller is measured, and the change after one year of use is investigated.

In addition, the amount of wear of the outer peripheral surface of the roll means the amount of wear of the outer peripheral surface of the roll after one year of use, and the maximum value when measuring the entire length of the roll.

In addition, the incidence of surface defects due to adhesion during use was investigated.

Moreover, as a comparative example, the same investigation was also made about the case where the conventional ceramic sleeve roll was used. In the conventional ceramic sleeve roll, the shaft portion is heat resistant steel and the roller body is tantalum nitride Si ₃ N ₄ is formed.

The above results are shown in Table 2. As a result, it can be seen that in the case of using a conventional ceramic sleeve roll, after 6 months of use, the roll is used. When the shaft portion is bent and the amount of the eccentricity of the roller is increased and exceeds the allowable range (1.5 mm or less), it is necessary to replace the roller after one year of use.

On the other hand, when the hearth roll of the present invention is used, the amount of the eccentricity of the roll is not changed after one year of use, and the amount of wear of the outer peripheral surface of the roll is at most 0.08 mm, so it is estimated from the above results. Roll life can easily reach more than 10 years.

Further, the incidence of surface defects of the product steel sheet caused by the adhesion of the hearth roll of the present invention is 6 months after the use of the hearth roll of the comparative example in which the shaft portion is heat resistant steel after one year from the start of use. The incidence is also better than the value.

5‧‧‧ hearth roll

5a‧‧‧Axis

5b‧‧‧roll body

Claims (9)

A hearth roll is a hearth roll for supporting and transporting steel sheets in a continuous annealing furnace, wherein the hearth shaft portion and the roller body of the hearth are composed of ceramics. The hearth roll according to the first aspect of the invention, wherein the hearth roll is formed of a different type of ceramic and is formed by a concentric circular ceramic layer centered on a rotating shaft of the roll. The hearth roll according to the first or second aspect of the invention, wherein the shaft portion and the roller body are made of different types of ceramics. The hearth roll according to any one of claims 1 to 3, wherein the roll body is composed of a different type of ceramic layer. The hearth roll according to any one of claims 1 to 4, wherein the ceramic has a high-temperature strength of 200 MPa or more and a thermal shock resistance of 350 ° C or more. The hearth roll according to any one of claims 2 to 5, wherein a coefficient of thermal expansion in a temperature range of use of the inner layer ceramic of the outer layer ceramic is in a range of 0.5 to 1.5. The hearth roll according to any one of claims 1 to 6, wherein the ceramic is tantalum nitride, tantalum carbide, aluminum oxide, and zirconium oxide. Either. A continuous annealing apparatus characterized in that the hearth roll according to any one of claims 1 to 7 is used for any one of a heating belt, a soaking zone, and a cooling zone. The continuous annealing apparatus according to claim 8, wherein the hearth roll is used in a heating zone, a soaking zone, and a cooling zone in a furnace at a temperature of 700 to 1300 °C.